[time-nuts] Windows XP time
Jim King
jim at jimking.net
Thu May 18 08:35:46 EDT 2006
Joseph Gray wrote:
>> The fundamental difference between SNTP and NPT is that SNTP does only a
>> period check and adjustment, so the clock can drift significantly
>> between polls. NTP on the other hand attempts to continuously steer the
>> clock, and uses a much more sophisticated algorithm to determine the
>>
> offset.
>
>> John
>>
>
> I knew SNTP was not as good as NPT, but I would have thought that SNTP kept
> the clock accurate to at least the nearest second. Obviously not. So, what's
> the worst that a typical PC clock would be off when using SNTP?
>
I've found that when Windows is behaving its SNTP client does a pretty
good job of keeping the system time within 100ms of an NTP server.
Here's a screenshot of NTPmonitor showing my office PC's time offset
overnight: http://flounder.jimking.net/~jim/files/ntpmonitor-boron.png
(The red line in the plot is the server that the PC is syncing with.)
At times, I have seen Windows timekeeping get squirrely, and in that
case I'll see large excursions. Most of the time it behaves pretty well.
A hint: For some reason the SNTP client needs/prefers/desires a ",0x1"
tacked onto the end of the SNTP server name. e.g. "net time
/setsntp:us.pool.ntp.org,0x1". Does anybody know exactly what the
",0x1" does?
My FreeBSD box with an M12 keeps much better time, of course. :)
Jim
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